Br. Radke et al., Parents' predicted transmitting abilities are not associated with culling prior to second lactation of Michigan, USA dairy cows, PREV VET M, 43(2), 2000, pp. 91-102
The objective of this study was to test the association between parents' pr
edicted transmitting abilities (PTAs) for milk fat and protein and subseque
nt culling of heifers during rearing or first lactation. The data from 1992
to 1996 consisted of the culling outcome of 5619 Michigan Holstein heifers
during rearing or first lactation, and the heifers' parents' PTAs from the
period in which the heifers were born, Fixed-effect probit models (both di
chotomous and ordered) estimated the relationships between culling and pare
nts' PTAs. Herd effect was modeled as a fixed-effect. There was no associat
ion between PTAs of milk, fat, and protein for each heifer's parents and su
bsequent culling of the heifer during rearing or first lactation. Weak evid
ence for the necessity of modeling the herd effect as fixed was present. Th
e lack of association between parents' PTAs and reason-specific culling (vo
luntary versus involuntary) - coupled with the counter-intuitive effects of
parents' PTAs on the probability of being culled for each of the reasons -
raised questions about the utility of classifying culling reasons accordin
g to the voluntary nature of the culling decision. We concluded that Michig
an producers are not using parents' genetics in heifer-culling decisions. (
C) 2000 Elsevier Science B.V. All rights reserved.